As described in, e.g., JP,A 9-178591, one conventional pressure sensor is constructed as follows. An outer casing unit comprises a connector section (1f) integrally formed with a connector terminal for electrical connection to the exterior, a frame (1d) having openings positioned in opposed two directions, a resin-made housing (5a) having a tubular pressure introducing section, which is projected from the inner side and is provided to orient in a direction toward the opening, a first resin-made cover (4) provided with a mount portion for mounting to the exterior, and a second resin-made cover (5) provided with a pressure introducing pipe. A sensor unit is constituted as a case including therein a semiconductor chip for converting pressure into an electric signal, the case being provided with a lead terminal for electrical connection to the exterior and a pressure introducing pipe. The sensor unit and the outer casing unit are assembled through the steps of bonding the sensor unit to the pressure introducing section of the housing, electrically connecting the lead terminal of the sensor unit to the connector terminal, assembling the first cover to the housing through a rubber-made packing, pouring a potting agent in a space, which is surrounded by the housing and the first cover and in which the sensor unit is disposed, and assembling the second cover to the housing with an adhesive, followed by thermo-setting of a resulting assembly.
With such a construction, however, because the outer casing unit is made up of a plurality of resin components, molds and molding steps for manufacturing the individual components are required, and an increased number of steps is also required for assembling the sensor unit and a group of those components of the outer casing unit. Accordingly, an increase of the cost is unavoidable. Another problem is that, because the number of joints is increased, a risk potential of failures possibly occurred while being handled in the market also increases. Furthermore, because the connector terminal for electrical connection to the exterior is integrally molded in the housing resin beforehand and a lead terminal joint portion of the sensor unit is projected into the housing frame, there is a limit in reducing the housing size. In addition, to tightly hold the joint between the lead terminal and the connector terminal, the steps of pouring and hardening a silicone resin and a potting agent are required, thus resulting in an increase of the cost.
Meanwhile, as described in, e.g., JP,B 6-84918, there is known a structure in which a pressure sensor unit (1) and a metal case (4) containing an IC (2) therein are integrally molded with a resin case (5). With such a structure, manufacturing steps can be simplified and the cost can be reduced.